Fuze initiated by spin rate decrease



April 1968 D. L. SWANSON 3,375,787

FUZE INITIATED BY SPIN RATE DECREASE Filed March 28, 1967 2 Sheets-Sheet 1 ,4 22 1 .5 45 14 6 F3 f i 2; 1

L; 72/ 14 19 g j '41 W 4; z

M/I dA/I'OA. 90/14/11. Mal/fa April 2, 1968 D. L. SWANSON 3,375,787

FUZE INITIATED BY SPIN RATE DECREASE Filed March 28, 1967 2 Sheets-Sheet United States Patent C) 3,375,787 FUZE INITIATED BY S IN RATE DECREASE Donald L. Swanson, Anaheim, Calif., assignor to Northrop Corporation, Beverly Hills, Califl, a corporation of California Filed Mar. 28, 1967, Ser. No. 628,221 7 Claims. (Cl. 102-79) ABSTRACT OF THE DISCLOSURE Briefly, my invention comprises an elongated fuze body mounted perpendicular to the spin axis, a detonator slide in the body held away from a firing pin by a lock member or by the centrifugal force of the spin, the lock member being ejected by the centrifugal force to permit alignment of the firing pin with the detonator slide. When the spin rate diminishes to a relatively low rate upon impact, a spring pushes the'detonator slide through the spin axis, whereupon the combination of spring force and centrifugal force in the opposite direction from before drives the slide into the firing pin.

The present invention relates to fuzes for munitions, and more particularly, to a time delay fuze adapted for use in spinning bombs, grenades, and the like wherein the fuze is set off by reduction of the spin rate to a predetermined value, and the main charge is exploded by ensuing fuze action.

Previous fuzes for spinning bombs, grenades, and the like 'have been complicated and unreliable, relatively unsafe, and inconvenient to install and make ready for operation. The objects of this invention are to provide a miniature sized fuze of the character described which is much simpler in construction and operation, and is easier to load than prior such devices. It is a further object to provide such a fuze which is inherently safe during and after loading until used. To effect the latter, another object of the present invention is to provide a fuze construction and combination which is not armed until the bomb or other explosive is started spinning and also has been dropped or separated from its carrying position. It is yet a further object to provide a fuze which will operate satifactorily in most all types of impact media, including jungles.

Other objects and advantages will become evident or will be pointed out in the detailed description to follow and in the accompanying drawings, from which my invention will be fully understood,

In the drawings, shown by way of illustration and not limitation:

FIGURE 1 is a plan view of the present fuze assembly.

FIGURE 2 is an enlarged end view of the fuze assembly.

FIGURE 3 is a longitudinal section view of the fuze assembly, taken as indicated by broken line 3-3 of FIGURE 2.

FIGURE 4 is a partial sectional view of the fuze, taken as indicated by broken line 4-4- in FIGURE 2, showing the firing pin in its safe position.

FIGURE 5 is a sectional view similar to FIGURE 4, showing the firing pin in its ready or armed position.

FIGURE 6 is an end view of the lock member.

FIGURE 7 is a sectional view of the lock member taken as indicated by broken line 7--7 in FIGURE 6.

FIGURE 8 is a perspective view of the rotor assembly carrying the firing pin.

FIGURE 9 is a plan view, partly in section, showing a slightly modified fuze assembly as installed in a typical bomb for which it has utility.

Referring first to FIGURES 1, 2 and 3 for a detailed description of a specific fuze embodiment, a generally cylindrical housing 1 contains a longitudinal bore 2, and a lateral bore 4 is provided through an enlarged end 5 of the housing 1. A rotor 6 fits loosely in the lateral bore 4, details of this rotor being further shown in FIGURE 8. It comprises two end hubs 7 and an eccentric center portion 9 formed by channeling through the rotor to a depth of more than one-half its diameter. A firing pin 10 is pressed into the base 11 of this center portion, to point back across the longitudinal center line of the rotor 6. The end hubs 7 each contain a through aperture 12 parallel to the extent of the firing pin 10. A tapered centering pin 14 fits loosely in each aperture 12, the length of pins 14 being slightly less than the rotor diameter.

A lock assembly 15 is slidably installed into the longitudinal bore 2 of housing 1 at its enlarged end 5, where it mates with the rotor 6 as shown in FIGURES 3 and 4. FIGURES 6 and 7 show that the lock assembly 15 comprises a partially sliced-01f cylindrical plunger 16 forming a flat surface 17, the latter having a central V-shaped groove 19 which accommodates the firing pin 10. The flat plunger surface 17 fits loosely against the rotor base 11 when both parts are in the housing 1.

Plunger 16 also contains a blind bore 20 carrying a lock spring 21 and two locking balls 22 and 23 very near the exterior surface 24 of the plunger 16. The open end of bore 20 is staked to retain the balls, and a side hole 25 is provided into the bore approximately midway between the illustrated position of the balls in FIGURE 7. Hole 25 is slightly larger than the ball diameter. When the lock assembly 15 is installed into housing 1 from the left-hand end, a tool may be inserted from the open right-hand end to force the end ball 23 partially through hole 25 and into an annular groove 26 in housing 1. When the end ball is then released in this position, the lock assembly 15 is obviously locked in the housing 1, as shown in FIGURE 4.

Next to lock assembly 15 in housing 1 is a detonator slide member 27 normally pressed against the lock assembly 15 by a firing spring 29 in turn held in place by a threaded end plug 30. Slide member 27 is hollow and contains the explosive fuze components. As shown in this embodiment (see FIGURE 3), the slide contains a staked-in detonator 31 and cup 32, a first fire composition 34, a time delay composition 35, a charge of lead azide 36, and a booster charge of a high explosive 37, such as cyclonite, for example. However, various pyrotechnic and explosive compositions may be used as desired in this detonator slide 27. The fuze is set off when the detonator 31 strikes the firing pin 10 as will be descn'bed later.

Approximately in the middle thereof, the fuze housing 1 is preferably provided with two diametrically opposed recesses 39 which are each loaded with a lead charge 40 of cyclonite for example, which as the name implies is to lead or augment the fracture of the housing 1 at an output position substantially centrally of whatever main charge of high explosives the fuze assembly is to detonate.

This fuze is intended for application in a spinning bomb or similar article. An example is shown in FIGURE 9. Here, a tune assembly 41 is installed along the axis symmetry of a bomblet 42, this bomblet having a generally cylindrical shape for example. The rotor 6 and lock 15 are assembled in the housing 1, and the housing has a flared right-hand end 44 to retain it in the bomblet 42.

The center of gravity of the complete bomblet and fuze is located at point P, and in this plan view, the bomblet 42 is designed to be spun about a vertical axis perpendicular to the plane of the paper, through P. The center of gravity of detonator slide 27 is at a point S lying to the right of P, or toward the firing spring 29. Thus, considering the bomblet to be in free fall and spinning as described, the detonator slide 27 will be moved against the firing spring 29 by centrifugal force and held in a position more to the right than that shown in FIG- URE 9.

In this free fall condition, the aforesaid spin will have ejected the lock assembly out of the left end of the fuze by virtue of the centrifugal force overcoming the force of lock spring 21 and thus allowing the locking ball 23 to be removed from the annular groove 26. As soon as lock assembly 15 has escaped, the rotor 6 will, under centrifugal force, rotate from the safe position as shown in FIGURE 4 to the armed position shown in FIGURE 5. At the same time, the centering pins 14- slide to the left and seat in retaining holes 45 located in the end of housing 1. Retaining holes 45 are smaller than the maximum diameter of pins 14 so that the pins 14 remain as shown in FIGURE 5, thus assuring that rotor 6 will not subsequently be jarred from its armed position.

When the bomblet 42 lands, its spinning rate obviously decreases rapidly. When the spin rate drops to a predetermined design value, the firing spring 29 pushes the detonator slide 27 toward the center, and as the center of rotation is crossed by the slide 27, the reversed centrifugal force and the firing spring together ram the detonator 31 against the firing pin 10. The bomb is then exploded according to the action of the selected fuze pyrotechnic and explosive ingredients contained in the slide 27.

Note that when slide 27 has struck firing pin 10, the booster charge 37 is approximately opposite the lead charge 40.

In one embodiment, the initial design spin rate is 300 revolutions per second, for example, and the fuze firing spin rate is 50 revolutions per second, for example. It is readily seen that with such a system, the fuze will not be prematurely actuated by collision with objects such as overhead trees for example, but will drop to a position of vertical rest before the spin rate decays to about 50 r.p.s.

The fuze assembly 41 of FIGURE 9 is modified somewhat from the shape as shown in previous views, by having the enlarged end beveled to form a central edge 46. Operation of the fuze is identical, however. This modified shape is for the purpose of adapting to a particular overall system where a plurality of bomblets 42 is radially arranged about the several edges of which edge 46 is typical, so that each lock assembly 15 is thus essentially butted against an adjacent lock assembly, and wherein the entire system is initially run up to speed about the edge 46 as axis. When spinning about an axis coinciding with edge 46, the detonating slide member 27 is retracted against its firing spring 29 as described hereinbefore, but the lock assembly 15 tends to be forced inwardly of the fuze assembly 41 instead of outwardly to start with, thus further assuring that it will not be accidentally released from the housing. When the entire cluster is simultaneously separated and released or dropped, then the individual bomblet 42 flies outwardly in a certain trajectory and assumes rotation about its own center of gravity P as described above. The arming cycle does not take place until the time of each unit bomblet rotation by itself. The slide 27 must of course still remain retracted until the spin rate has decreased to the required firing value.

This application as in FIGURE 9 is only an example, however, since the fuze of the present invention can obviously be used in other devices, Also, it will be noted that the fuze itself may be spun about other axes, such as the axis XX in FIGURE 9 which passes through point P perpendicular to the axis described previously. In general, it may 'be stated that the center of gravity S of the slide member 27 will be located to the right of the center of gravity of the fuze assembly 41, as illustrated, although the opposite could be true if the fuze assembly is installed in a package wherein the overall spin axis is to the left of the center of gravity S of the slide 27.

When the present fuze is to be used in a single body which is spun solely about an individual axis of rotation of its own, the slide 27 must move to the right against its firing spring 29 under less centrifugal force than it takes to unlock and eject the lock assembly 15, so that the slide 27 will not follow the lock assembly out at the same time.

It is thus seen that a simple and reliable fuze action has been assured. Especially it will be noted that no friction affects the firing time of the fuze, i.e., the friction forces on the detonator slide which strikes the firing pin are zeroed out by the spinning action. This new principle eliminates a very troublesome factor in previous fuze linkages and mechanisms.

While in order to comply with the statute, the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

What is claimed is:

l. A fuze assembly comprising:

(a) a housing having a longitudinal bore therein and a lateral bore intersecting said longitudinal bore near one end of said housing;

(b) a rotor, in said lateral bore, having a cut-away center section forming an eccentric base, and a firing pin extending from said base near the center of said rotor, said rotor having a safe position where said eccentric base is rotated to one side of said longitudinal bore and said firing pin points crosswise of said housing, and said rotor having an armed position, rotated from said safe position, where said firing pin points axially of and toward the center of said housing, the mass of said eccentric base acting in the direction to swing said rotor from its safe position to its armed position under an external force on said rotor toward the center of said housing;

(c) a lock member slidable in said longitudinal bore and mating with said rotor base where said lock member crosses said rotor to hold said rotor in its said safe position, locking means in said lock member normally holding said lock member in a locked lengthwise position in said longitudinal bore, said locking means being releasable under a predetermined axial force acting on said lock member in a Withdrawal direction;

(d) a detonator slide, in said longitudinal bore, having a detonator in one end thereof normally resting against the inside end of said lock member;

(e) a firing spring in said longitudinal bore urging said slide toward said rotor;

(f) said lock member and said slide being arranged relative to the center of gravity of said fuze assembly such that when said assembly is spun rapidly about a lateral axis through its center of gravity, said slide is forced to move against said firing spring away from said lock member, and said locking means is released to allow said lock member to slide out of said housing.

2. Apparatus in accordance with claim 1 wherein said longitudinal bore extends completely through said housing, allowing installation of said detonator slide and said firing spring from the end opposite said lock member, and including a removable end plug therein holding said firing spring in place.

3. Apparatus in accordance with claim 1 wherein said detonator slide further includes a time delay composition ignited by said detonator, and a booster charge ignited by said composition to provide a rupture of said housing adapted to set off a main charge adjacent said fuze assembly.

4. A fuze assembly comprising an elongated hollow housing; a detonator slide and a lock member slidable in said housing; elastic means normally urging said slide toward said lock member; locking means normally locking said lock member in said housing; a firing pin carried in said housing near one end thereof; said lock member positioned to normally hold said slide away from said firing pin; said slide and said lock member being arranged relative to the center of gravity of said fuze assembly so that when said assembly is spun rapidly about an axis through said center of gravity perpendicular to the sliding direction thereof in said housing, said detonator slide is moved against said elastic means, said locking means is unlocked, and said lock member is thrown out of line between said detonator slide and said firing pin to thereby arm said fuze assembly; a rotor member having an eccentrically weighted portion carrying said firing pin fixed thereto, said rotor mounted for rotation about an axis perpendicular to the sliding direction of said lock member, said lock member having a fiat side, said rotor having a safe position where said flat side maintains said rotor with said eccentrically weighted portion located toward the side of said housing, and said rotor having an armed position where, in the absence of said lock member, said eccentrically weighted portion swings said firing pin into alignment with the sliding direction of said detonator slide when said assembly is spun as recited.

5. A fuze assembly comprising an elongated hollow housing; a detonator slide and a lock member slidable in said housing; elastic means normally urging said slide toward said lock member; locking means normally locking said lock member in said housing; a firing pin carried in said housing near one end thereof; said lock member positioned to normally hold said slide away from said firing pin; said slide and said lock member being arranged relative to the center of gravity of said fuze assembly so that when said assembly is spun rapidly about an axis through said center of gravity perpendicular to the sliding direction thereof in said housing, said detonator slide is moved against said elastic means, said locking means is unlocked, and said lock member is thrown out of line between said detonator slide and said firing pin to thereby arm said fuze assembly; said housing having a longitudinal bore carrying said detonator slide and said lock member; a lateral bore intersecting the axis of said longitudinal bore at substantially a right angle, near one end of said housing; an eccentrically weighted rotor carrying said firing pin and rotatable in said lateral bore; said lock member normally resting slidably against the center portion of said rotor when the latter is turned to a safe position, and said rotor adapted to rotate to an armed position across said longitudinal bore in the absence of said lock member.

6. Apparatus in accordance with claim 5 including positioning means associated with said housing and said rotor to hold said rotor in said armed position, said positioning means being operative in response to spinresultant forces as said fuze is spun as recited, when said rotor reaches said armed position.

7. A fuze assembly comprising an elongated hollow housing; a detonator slide and a lock member slidable in said housing; elastic means normally urging said slide toward said lock member; locking means normally locking said lock member in said housing; a firing pin carried in said housing near one end thereof; said lock member positioned to normally hold said slide away from said firing pin; said slide and said lock member being arranged relative to the center of gravity of said fuze assembly so that when said assembly is spun rapidly about an axis through said center of gravity perpendicular to the sliding direction thereof in said housing, said detonator slide is moved against said elastic means, said locking means is unlocked, and said lock member is thrown out of line between said detonator Slide and said firing pin to thereby arm said fuze assembly; said locking means comprising an annular groove in an inner circumference of said housing; a bore in said lock member carrying a spring and a locking ball, and a side hole in said lock member intersecting said bore at a position adjacent said groove; said locking ball protruding through said side hole into said groove under the force of said spring to define a locked position of said lock member; and said spring being designed to be overcome by force resulting from said spin, to allow said ball to drop back inside said lock member and thus allow it to slide away.

References Cited UNITED STATES PATENTS 1,363,079 12/1920 Bergman 102-79 1,507,184 9/ 1924 Ianecek 10279 X 2,434,971 1/ 1948 Thibodeau 102-79 3,146,714 9/1964 Moore 10279 X BENJAMIN A. BORCHELT, Primary Examiner. G. H. GLANZMAN, Assistant Examiner. 

